1. Field of the Invention
The present invention concerns a control circuit for a bistable solenoid which can be used particularly, but not exclusively, in an electromagnetic relay, in a magnetic control electromagnet, for example for clamping or releasing of a lock, or even in a bistable electrovalve.
It should be borne in mind that a bistable solenoid usually consists of a magnetic circuit acting on a mobile armature in order to lead it to one or other of the following two stable positions:
a first position R corresponding to a maximum reluctance of the magnetic circuit, and PA1 a second position S corresponding to a minimum reluctance of the magnetic circuit. PA1 a permanent magnet which polarizes the magnetic field inside the circuit, in the absence of any external field, and PA1 at least one coil which, when crossed by a current, creates a field which entrenches itself or is added to the one created by the magnet. PA1 the single coil solution does not enable a reverse-lock diode to be inserted inside the circuit of this coil, PA1 the two coil solution requires either the number of matrix lines or colums to be doubled. PA1 a first voltage zone including the voltage level of pulses S of the first type, PA1 a second voltage zone including the voltage level of pulses R of the second type, and PA1 a third voltage zone included between the levels of the two types of pulses R, S, and where the amplitude of the said pulses must never occur.
These two positions are usually denoted by the terms "RESET", as regards the first, and "SET" as regards the second.
The magnetic circuit enabling these two positions to be obtained generally includes:
Control of these bistable solenoids is carried out using pulses, the duration of which must be sufficient in order that the mobile armature and mobile equipment connected to it take up the sought after stable position.
When the bistable solenoid includes only one coil, it is necessary to invert the polarities at the terminals of this coil so as to obtain the two sought after stable positions S and R.
On the other hand, where the solenoid includes two coils connected in series and to each other through a middle point, the pulse intended to obtain position S is applied to the terminals of one of the coils, whilst the pulse intended to obtain position R is applied to the terminals of the other coil, the middle point between the two coils capable of being permanently connected to one of the two feed coils.